This invention relates to exhaust gas equipment and, more particularly, exhaust gas equipment for an internal combustion engine having an exhaust pipe, an exhaust gas cleaner located in the exhaust pipe and having an adsorption filter. Exhaust gas is admitted to the filter body under the control of an exhaust gas butterfly.
Exhaust gas equipment of the generic type is known from Japanese patent document JP 62-162715. In the exhaust gas equipment described in that reference, an auxiliary pipe branched off from an exhaust pipe contains an adsorption filter which has flow directed to it in the cold starting phase of the internal combustion engine. The flow is directed to it by deflecting the exhaust gas by means of an exhaust gas butterfly located in the branch of the exhaust pipe. After the catalyzer has taken up its function, the exhaust gas flow is substantially guided through the exhaust pipe by controlling the butterfly and, particularly in full-load operation, this exhaust pipe becomes very hot. In the case of small installation spaces, three-dimensionally extensive auxiliary pipes are difficult to achieve so that the adsorption filter and the exhaust pipe are located close together. Because of this, however, the adsorption filter can rapidly become overheated and therefore damaged.
There is therefore needed exhaust gas equipment of the generic type developed in such a way that damage to the filter due to overheating is avoided in an arrangement which is economical in installation space.
This need is met according to the present invention by exhaust gas equipment for an engine having an exhaust pipe, an exhaust gas cleaner located in the exhaust pipe and having an adsorption filter. Exhaust gas is admitted to the filter body under the control of an exhaust gas butterfly. The adsorption filter is located along the course of the exhaust pipe with a filter body surrounding the exhaust pipe coaxially. A thermal insulation element is provided between the filter body and the exhaust gas flow. For guiding the exhaust gas flow through the filter body, the thermal insulation element has transfer openings at least partially outside the exhaust pipe section surrounded by the filter body.
The adsorption filter is located along the course of the exhaust pipe and its filter body surrounds the latter coaxially. It therefore presents a very compact configuration which is economical in installation space. In order to protect the filter body from overheating, a thermal insulation element is provided between the filter body and the exhaust gas flow. For guiding the exhaust gas flow through the filter body, the thermal insulation element has transfer openings at least partially outside the exhaust pipe section surrounded by the filter body. The thermal insulation element is then intended to possess the property of attenuating the high temperature effect of the exhaust gas on the filter body to the extent that although the latter is heated, damaging temperatures are not reached. This has the advantage that at the end of the cold starting phase, the filter body already possesses a sufficiently high temperature for the pollutants absorbed by the filter body to evaporate so that the regeneration period of the adsorption filter is shortened.
In an advantageous embodiment of the invention, the thermal insulation element is designed as a thermal insulation tube. Large-area thermal contact between the exhaust gas flow and the filter body is achieved by means of the large area of the thermal insulation tube so that rapid and even heating of the filter body and, in consequence, particularly good regeneration of the adsorption filter, is achieved.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.